WO1998013892A1

WO1998013892A1 - Fuel cell installation with tubular high temperature fuel cells

Info

Publication number: WO1998013892A1
Application number: PCT/EP1997/005143
Authority: WO
Inventors: Wolfgang Winkler
Original assignee: Wolfgang Winkler
Priority date: 1996-09-26
Filing date: 1997-09-19
Publication date: 1998-04-02
Also published as: DE19639517A1; EP0870343A1

Abstract

The invention concerns a fuel cell installation (30) with high temperature fuel cells. The fuel cells are rotationally symmetrically designed as cell elements (1). Combustion air as cathode gas (2a) inside on the cathode side (2) and fuel gas as anode gas (3a) outside on the anode side (3) is applied. Outside on the anode side the fuel cells come into full contact with a high-temperature stable conductive metal felt such as nickel felt (4) or the like, thus forming a voltage plane.

Description

Fuel cell device with tubular high-temperature fuel cells

The invention relates to a fuel cell device with tubular high-temperature fuel cells. Fuel cells are increasingly being used for the direct generation of electricity from the combustion reaction of the fuel in energy technology. The largely isothermally available cell waste heat with cell temperature can be used for further electricity generation in a thermal power process if the fuel cells are operated at high temperature (high-temperature fuel cells). This gradual use of the thermodynamic potential of the combustion reaction by means of the combination of the fuel cell and the thermal power process means that electrical efficiencies of up to 80% can be expected. {Winkler W.: Possibilities of designing combined cycle power plants with high-temperature fuel cells. BWK 44 (1992) No. 12, pp. 533-538; Winkler W. Analysis of the system behavior of power plant processes with fuel cells. BWK 45 (1993) No. 6, pp. 302-307; Winkler W.: The influence of process configuration on the working capacity of

Internal combustion processes. BWK 46 (1994) No. 7/8. Pp. 334 - 340). A prerequisite for these high efficiencies is a suitable external cooling of the cells including an integration of the endothermic fuel preparation (see Winkler W.: SOFC-Integrated Power Plants for Natural Gas. Proceedings is European Solid Oxide Fuel Cell Forum. Ulf Bossel. Lucerne. 1994. ISBN 3-922148- 14-XS 821 -848 and Winkler W.: Principles of the design of combined fuel cell power plants. VDI report 1174. "Energy supply with fuel cell systems - status and prospects". VDI Verlag Düsseldorf. 1995. S 131 - 154.). Natural gas reforming, allothermal coal gasification or biogas production can be considered as endothermic processes for fuel processing.

A particularly promising development is the oxide ceramic fuel cell (SOFC = Solid Oxide Fuel Cell) in a tubular construction. In the tubular fuel cell, one electrode is on the inside and the other on the outside of the fuel cell tube, both electrodes being electrical and separated on the gas side but connected to one another with regard to the transport of oxygen ions. The term "electrical" refers here and below to the transportation of Electrons. All materials used must have approximately the same thermal expansion in order to avoid inadmissible thermal stresses. Air is applied to the cathode and fuel gas to the anode. The individual cells are used to build structures, stacks or stacks, which are suitable for use in power plants. The fuel cells are electrically connected in series to achieve technically usable voltages. A simultaneous parallel connection of the individual cells or stacks of the same voltage level ensures the necessary redundancy in the event of failure of individual cells or stacks. A step-by-step combustion of the fuel gas in cells connected in series (cascading) ensures that, as far as advanced concepts are concerned, the working capacity of the fuel gas is utilized as much as possible.

So far, essentially two basic forms of constructive solutions for tubular cells are known. On the one hand, smaller, ring-shaped cell elements are connected to form tube cells by means of connecting contacts (interconnectors), which make electrical contact between the anode and cathode electrodes of the cell elements in a gastight manner. The structure is reminiscent of the welded connection of seamless pipes (see e.g. old Domier concept & MHI concept: Dönitz W., Erdle £., Streicher R: Oxide ceramic fuel cells, principle, development status and market opportunities in H. Wendt υ. V. Plzak (Ed.): Fuel cells - state of the art development lines market opportunities. VDI Verlag Düsseldorf. 1990. S 133 - 143. & Yoshioka T. et. Al.: Development on tubular Type SOFC Module. Proceedings 2nd IFCC Kobe 1996. pp. 251 - 254 ). Here the fuel gas is supplied inside and the combustion air outside. The cascading of the combustion control follows from the constructive training. An electrical connection of the cells of the same voltage level to ensure the necessary redundancies for the current flow in the event of failure of a cell element is not possible with these concepts. An arrangement known from US-A-52 73 839 is based on a chain of annular cells, the anode and cathode sides of which are electrically connected to continuous supply tubes for fuel gas and air. Afterburning devices are arranged between the individual cell sections. A cascaded combustion and A serial electrical connection of the cells lying one behind the other on the flow side is not possible.

The second u.a. The solution known from US-A-5 273 839 is based on an electrolyte which is open in the longitudinal direction of the tube and which forms the necessarily gastight tube only when the connection is made (see Westinghouse concept, for example in: The Westinghouse solid oxide fuel cell program - A 1992 progress report, Westinghouse Electric Corporation, Pittsburgh, 1992). The cathode is applied to the inside of the tube and is contacted via the connection contact. On the outside, the anode is applied with corresponding openings so that there is no electrical connection to the connection contact. The tube is closed on one side. The construction is reminiscent of a longitudinally welded tube and the cell is not rotationally symmetrical. The combustion air is introduced into the cell tube near the closed end through an internal ceramic tube and flows out along the cathode side of the cell. However, this means that the diameter of the fuel cell tube is limited downwards and thus the power density is limited upwards. The fuel gas is supplied outside. The individual cells are connected in series via the contacting of a cell through the connection contacting with nickel felt on the anode side of the next cell. By adding the fuel gas in the direction of flow of the electric current, this construction also enables cascading. The desired redundancy can be achieved by contacting the individual cells of the same voltage level with nickel felt on the anode side. The electrolyte does not form a closed tube and the fuel cell is therefore no longer rotationally symmetrical. The contacts made on the outside of the tube relate to a total of three voltage levels. The inner tube for air supply limits the tube diameter downwards and thus the power density upwards. Serial electrical connection and cascading is only possible with several pipes.

The object of the invention is to design the construction of the fuel cell and the stack so that the serial circuit and the cascading in one Fuel cell tube is made so that the parallel connection of the individual voltage levels takes place in a stack, that the fuel cell tube and its components on the outer surfaces that are important for production and handling are completely rotationally symmetrical even during the production steps, that there is a downward design limitation of the diameter of the fuel cell tube does not exist and that the stack ensures the favorable integration of the required external cooling of the fuel cell tubes. The term stack also refers here to an arrangement of fuel cell tubes connected in parallel.

According to the invention, the object is achieved by the characterizing features of claim 1. Advantageous embodiments of the invention are described in the dependent claims.

According to the invention, the electrodes on the outside of a rotationally symmetrical high-temperature fuel cell element, hereinafter also referred to as a fuel cell element or cell element for short, are electrically conductively connected to one another by a felt that is resistant to high temperatures and thus form a single voltage level of parallel-connected cell elements; the electrodes of the inner sides of the parallel connected fuel cell elements of a voltage level are electrically connected to the electrodes of the outer sides of the corresponding fuel cell elements of a further voltage level by gas-tight connection contacts, the respective outer spaces of the parallel connected cell elements of both voltage levels filled with the electrically conductive felt by electrically insulating but gas-permeable intermediate floors or other suitable gas-permeable separating elements are separated in order to avoid short circuits. The number of voltage levels that are electrically connected in series is determined by the desired design voltage of the stack. The electrically connected in series with the gas-tight connection contacts

Fuel cell elements form the finished fuel cell tube. The main flow direction of the fuel gas and the combustion air is parallel to the pipe axis. A preferred form of training is the direct current arrangement and Another form of training is the countercurrent arrangement. A uniform distribution of the fuel gas flow is ensured by means of resistance elements at the inlet and / or by means of fuel injection at several points. To simplify matters, the gas flow on the anode side is also referred to as anode gas and on the cathode side also as cathode gas, regardless of the type of local gas composition.

In a preferred embodiment, the cathode side that is exposed to air lies on the inside and outside the anode side that is exposed to fuel gas and that is contacted with nickel felt or another material with a similar structure. If only nickel felt is used in the following, another material with a similar structure is also included, i.e. an electrically conductive felt resistant to the high temperatures of the fuel cell.

Another embodiment is the formation of the outside of the cell elements of the fuel cell tube as a cathode. Felts with fibers made of cathode material are used for contacting. The rest of the description refers to the design with the external anode side and the contact with nickel felt, since there is no difference in the construction of the two variants, apart from the exchange of the gas flows and the necessary other materials for the felt.

Fuel cell elements of different voltage levels are preferably connected to one another in a gas-tight manner by means of annular connection contacts, the cathode side of the fuel cells of the first voltage level and the anode side of the fuel cell of the next voltage level in the flow direction of the fuel gas being conductively connected to one another via the connection contacts. The fuel cells / ears are softly stored in the nickel felt surrounding them and are not braced with the intermediate floors, but the intermediate floors allow slight compensatory movements. The fuel cell tubes of the stack are expediently fitted gas-tight at their ends facing the inlet side in a perforated plate. In this way, the passage of air to the anode side of the fuel cells is prevented. In a preferred embodiment, the perforated plate consists of electrically conductive material with the same thermal expansion as the material of the fuel cells and is conductively connected to the anodes of the fuel cells and the contacting nickel felt. In a further embodiment, the series connection of the fuel cell elements begins with a cathode-ready contact on the perforated plate, insulation being provided between the perforated plate and the nickel felt

On the outlet sides of the gases, the fuel cell stacks are preferably designed such that both gas flows are routed separately to a post-combustion chamber. In particular, nozzle-shaped outlet connection contacts are provided on the outlet sides of the fuel cell tubes, which establish a conductive connection for current dissipation of the fuel cell stack. Precautions have been taken in the arrangement and design of the outlet nozzles that largely avoid the formation of nitrogen oxides during exhaust gas combustion.

The connection between the outlet connection contacts of the fuel cell tubes at the stack outlet by means of nickel felt is preferably designed such that anode gas is constantly present in the area. This makes oxidation impossible. Additional current leads are preferably movably arranged within the nickel felt to a certain extent in order to reduce the electrical resistance of the current leads. At the anode-side outlet there is an electrically conductive nozzle base or a conductive network in the stack.

With the counterflow arrangement, the fuel gas is added in the area of the air outlet. The exit area of the combustion air is designed such that the area of the current discharge on the cathode side - gas-tight - separates the area of the anode side of the fuel cell tubes lined with nickel felt and the exit area on the cathode side to prevent a gas mixture The fuel gas flow takes place against the flow of the combustion air towards the air inlet. This is where the anode-side exhaust gas generated during combustion is deflected. Channels conduct the anode-side exhaust gas to the air outlet area and to the afterburning chamber. Another embodiment of the counterflow arrangement allows separate removal of the anode-side exhaust gas and the exhaust air from the cathode side, an air box being provided at the outlet of the fuel cell tubes for collecting the cathode-side exhaust air. The exhaust air and the anode-side exhaust gas are removed via separate channels.

It is advantageous to adapt the lengths of the individual fuel cell elements of the fuel cell tube and thus their surface to the degree of utilization of the fuel gas in such a way that the surfaces increase with increasing degree of utilization of the fuel gas.

The stack is closed to the outside by solid walls. To prevent short circuits between the individual voltage levels, continuous ceramic walls or combinations of metallic walls with ceramic insulation pieces are preferably provided in the transition area between the voltage levels.

It is advantageous to design the respective stack similar to a flat burner. Other embodiments of the stack floor plan are circular and ring-shaped or hexagonal. In all of the above-mentioned embodiments, the afterburning chamber is designed in particular as a common combustion chamber. The combustion air is supplied via the supply line and air box to the cathode side of the fuel cell tubes. In an expedient embodiment, the fuel gas is supplied laterally at several points via a fuel gas line and or via separate nozzles in the perforated plate of the respective stack. This design allows the stack floor plan to be adapted to various required floor plans. It is advantageous if the cooling tubes are designed as radiation coolers and are made of electrically insulating material, as a result of which short circuits are avoided. A useful further development of the invention is the use of cooling tubes which are integrated in the stack parallel to the cell tubes.

Part of the heat released in the fuel cell stack is preferably immediately available for the endothermic process of fuel processing and or another part of this heat is provided for preheating the combustion air and or reheating cooled exhaust gas for further use in downstream processes. Corresponding catalyst material is provided in the tubes for the cooling tubes which are used for fuel processing.

A further developed embodiment of a cooler integrated in the stack consists of an electrically insulating tube, which is closed on the outlet side of the stack and is arranged in central locations parallel to the heat-supplying fuel cell tubes in the stack Open pipe arranged, which supplies the arrangement with cooling gas. The inner pipe is arranged centrally in the outer pipe so that the annular gap created between the pipes is sufficient to ensure that the cooling gas flows out functionally. In one variant, the cooling gas is combustion air, which after heating up flows into the air box and then to the cathode side of the fuel cell tubes. In the other variant, natural gas or another hydrocarbon-containing fuel gas is the cooling gas. Here, the tube arrangement, in which the pre-reforming now takes place, is provided with catalyst material and the previously reformed fuel gas flows through suitable openings in the outer tube, which are arranged on the inlet side of the stack, to the anode side of the fuel cell tubes.

An expedient development of the invention also uses the heat released in the afterburning for the fuel preparation and / or the air preheating and / or the reheating of the flue gas for use in downstream processes. Coal or biomass gasification can be provided in an allothermal gasification, the tubes heated by the stacks and / or the afterburning chamber serving as a heat source.

To produce the fuel cell tube, it is advantageous to use a continuous, porous carrier tube made of non-conductive material with the same thermal expansion as the electrolyte and to apply the individual fuel cell elements with coatings of cathode, electrolyte and anode material to the carrier tube by means of suitable thin-film or sintering technology. The individual cell elements which are formed one behind the other in this way are electrically connected in series by means of suitably applied gas-tight connection contacts.

An expedient further development of the invention is a partially electrically conductive carrier tube, which consists of a chain of tube elements made of cathode material, which by means of ring-shaped elements made of electrically insulating material with the same

Thermal expansion like the electrolyte with a suitable joining technique to that

Tube are connected. The outer surfaces of the tube elements are provided with a thin gas-tight layer of electrolyte material except for a small annular section at the end of each tube element made of cathode material, which remains free as a connection. The portion of the electrolyte material

The pipe surface is coated with anode material. The individual cell elements that are formed one behind the other are electrically connected in series by means of suitably applied gas-tight connection contacts in order to form the fuel cell tube. The part of the

Cathode connected to the anode of the next tubular element.

It is advantageous to design the tubular elements from cathode material in such a way that the conductor cross section of the tubular element increases due to internal ribs. With the same conductor cross-section, this permits thinner wall thicknesses of the construction and thus smaller diffusion paths for the combustion air and, during start-up operations, higher permissible temperature change rates than is possible with ordinary pipes. That to build the partially electric conductive support tube necessary annular element made of electrically insulating material is designed so that it is provided on both sides with a number of pin-shaped fitting elements which are fitted into the inner ribs of the tubular element made of cathode material and are equipped with suitable technology.

Another advantageous further development of the invention is the formation of gas channels parallel to the fuel cell tubes in the external nickel felt, inner rings or porous tubes made of nickel material being introduced in such a way that they exert a slight contact pressure on the nickel felt when heated and thus the contact between the nickel felt and the anode side of the Improve fuel cell tube.

A further advantageous development of the invention is the production of individual voltage levels, each provided with the associated gas-permeable intermediate floors, consisting of the required number of cell elements, nickel felt and inner rings which, when soaked in volatile plastic or water glass, result in a compact block. The gas-tight cell elements are designed so that they are equipped with a contact surface on the cathode and anode, as well as the necessary insulation. The assembly into the fuel cell tubes is then carried out in all tubes of the stack in one operation per voltage level by connecting the associated cell elements to one another in an electrically serial and gas-tight manner using a suitable joining method.

The invention is described in more detail below with reference to the exemplary embodiments shown schematically in the drawings, from which further details, features and advantages result.

It shows:

1 shows part of a fuel cell device in section, 2 shows a fuel cell device with tubular fuel cell elements connected in series in section,

3a shows a fuel cell device with an arrangement for the supply of fuel gas in countercurrent,

3b shows a fuel cell device with an arrangement for the supply of fuel gas in direct current,

Fig. 4 shows a fuel cell device with a fuel gas supply in

Direct current and numerous stacks of fuel cell tubes,

5 shows a fuel cell device with fuel cell tubes and

Stack of integrated coolers on average,

Fig. 6 shows part of the fuel cell device as a section

Fuel cell tube with carrier tube,

7a a part of the fuel cell device as a section of a partially electrically conductive support tube,

7b shows a part of the fuel cell device as a section of a fuel cell tube with a partially electrically conductive carrier tube,

8a shows a part of the fuel cell device as a cross section of a cathode tube provided with inner fins,

Fig. 8b a part of the fuel cell device as a section of the electrically non-conductive connecting elements of a partially electrically conductive support tube and the fit into the inner ribs of the

Tubular element made of cathode material, Fig. 9 is a sectional view through part of the fuel cell device with anode-side gas channel and pressure rings of the nickel felt contact.

1 shows a fuel cell device 30 of a basic type of rotation-symmetrical high-temperature fuel cells (SOFC) have inner cathodes 2 and outer anodes 3 on the circumference, which are separated by the electrolyte 23. The fuel cells are preferably designed as tubes. The cell elements 1 are acted upon on the inside on the cathode side with air, which is denoted by 2a, and on the outside on the anode side with fuel gas, which is denoted by 3a. The arrows 2a, 3a point in the direction of flow. 1 is rotationally symmetrical with respect to a central axis S. On the anode side, the cell elements 1 are contacted by a high-temperature-resistant, electrically conductive metal felt, which is, in particular, nickel felt 4. Instead of nickel felt 4, another material with a similar structure can be used. A voltage level is formed by the electrically conductive connection of cell elements 1 arranged in parallel on the same spatial level. This concept has the advantage that the anode space with the porous layer of nickel felt 4 or the like. Contacting material can be filled without paying particular attention to the location of the felt. The main flow direction of the fuel gas is parallel to the tube axis S, which means that both a cocurrent and a countercurrent arrangement is possible. A uniform distribution of the fuel gas flow is ensured by appropriate resistance elements at the inlet and / or by fuel injection at several points in a fuel cell stack. The structural design of the stacking element of a stress level is thus defined.

To build a stack, a separate supply and discharge of the gas streams on the sides of the anodes 3 (fuel gas and reaction product gas 3a) and cathodes 2 (combustion air and exhaust air 2a), the electrical wiring, the cascading, so that the structure of the fuel cell tube 100 and the afterburning of anode and cathode exhaust gas, as well as the integration of the fuel gas preparation and the stack cooling. In the further the gas flow on the anode side is also referred to as anode gas 3a and on the cathode side also as cathode gas 2a, regardless of the type of local gas composition.

Cascading can be achieved very easily by connecting stack elements of several voltage levels to one another in such a way that the elements are electrically connected in series. The individual cell elements 1 are gas-tightly connected with annular connection contacts 5 such that the cathodes 2 of the stacking element n are contacted with the anodes 3 of the stacking element n + 1 via the connection contacts 5. The connection contact material (e.g. lanthanum chromite) must be electrically conductive and chemically stable at the operating temperature and have the same thermal expansion as the electrolyte material (ytterium-doped zirconium oxide). The individual row elements 1 connected in series form the fuel cell tube 100, through which air flows. So that no short circuit occurs in the stack, it must be ensured that the anode sides of the individual stack elements are electrically separated from one another. At the same time, however, the fuel gas or the gas mixture of fuel gas and product gas must flow freely from one stacking element to the next.

This is achieved according to the invention in that a gas-permeable intermediate floor 6 made of insulator material, which is designed, for example, as a nozzle bottom, is inserted with corresponding passages for the fuel cell tubes 100 between the individual stacking elements or spacers made of insulator material are used which prevent a short circuit between two voltage levels. It is expedient that the fuel cell tubes 100 are not clamped by these intermediate floors, but rather can move as freely as possible in order to rule out possible expansion problems from the outset. It is advisable to use zirconium oxide as the insulator material. This ensures the function of cascading and the anode-side parallel connection of the individual voltage levels within the stack. The electrical and gas connection of the stack to the overall system remains to be solved. Fig. 2 shows the stack structure. For this purpose, the cell elements 1 of the first group of stacking elements on the air side are fitted gas-tight in a perforated plate 7 such that the cathode gas 2a can flow into the fuel cell tubes 100 without coming into contact with the anode gas 3a. The perforated plate 7 consists of electrically conductive material with the same possible thermal expansion as the SOFC (eg lanthanum chromite) and is conductively connected to the anode 3 of the SOFC. In a further solution, the serial connection of the cell elements 1 on the perforated plate 7 begins with a correspondingly modified connection of the cells with a cathode-side contact. Insulation between perforated plate 7 and nickel felt 4 is provided.

The exit of anode gas 3a and cathode gas 2a from the stack is then designed such that both gas flows flow to the afterburning chamber 8. For this purpose, the anode gas space is initially electrically insulated from the outside by a gas-permeable intermediate floor 9 or spacers made of insulator material. The electrical current generated in the stack can then be tapped off on the cathode side. For this purpose, the cathode side of each fuel cell tube 100 is provided for contacting with the nozzle-shaped outlet connection contacts 10. These outlet connection contacts 10 at the pipe outlet establish the connection to the current conductor 11 of the stack via the nickel felt 4. This connection is arranged between outlet connection contact 10 and adjacent fuel cell tubes 100 in such a way that it is always wetted with anode gas 3a and therefore oxidation is excluded. This also allows the use of nickel felt 4 or the like as a material for current dissipation. This type of construction has the advantage of a movable mounting of the fuel cell tubes 100 at the outlet and avoids largely unintentional forces on the fuel cell tubes 100. Additional rigid current leads can be movably attached within the nickel felt 4 in order to minimize the resistance of the lead. To the outside, the construction is completed by the conductive nozzle floor or a conductive mesh 12. The outlet connection contact 10 and the conductive nozzle base 12 are designed and arranged in such a way that nitrogen oxide formation during the combustion of the anode exhaust gas is largely avoided. According to Fig. 3a, the anode gas 3a is added as a fuel gas in the counterflow arrangement in the area of the air outlet and the outlet area of the combustion air is designed such that the current discharge on the cathode side - gas-tight - separates the cell area and the outlet area so that a mixture of anode exhaust gas and fresh fuel gas is excluded. The fresh fuel gas flows against the flow of the combustion air in the direction of the air inlet. This is where the exhaust gas product generated during combustion is deflected. Channels guide the exhaust gas product to the air outlet area and to the afterburning chamber 8. Another embodiment of the counterflow arrangement, which is shown in broken lines in FIG Collection of the cathode-side exhaust air is provided. The exhaust air 2b and the anode-side exhaust gas 3b are removed via separate channels. The direct current arrangement, which has already been described above, is shown in FIG. 3b.

The stack must be terminated towards page 13 in such a way that no short circuit can occur between the individual voltage levels. This is solved by continuous ceramic walls. A combination of metallic walls with ceramic insulation pieces in the transition area between the individual voltage levels is another solution.

The stacks formed in this way have a modular structure and their size can be designed in such a way that the cooling of the stack from the outside is ensured by suitable heat exchanger devices which can be used to heat the working fluid in a downstream thermal power process or to heat another parallel or downstream endothermic process is.

4 shows an example of this in a direct current arrangement. Combustion air as cathode gas 2a comes from a supply line 14 to air box 16 and from there enters the cathode side of fuel cell tubes 100. The fuel gas as anode gas 3a is fed laterally into the stack 17 via the fuel gas line 15. The stack 17 is constructed here similar to a flat burner and the post-combustion chamber 8 is designed as a common combustion chamber. The size of the individual stacks is determined by the cooling conditions in order to ensure that the stacks are operated as isothermally as possible. In this arrangement, the cooling tubes 18 are arranged as radiation coolers. Another possible variant is an integration of the cooling tubes parallel to the fuel cell tubes 100 in the stack 17 itself. The cooling tubes 18 must, however, consist of insulator material in order to avoid short circuits in the stack. A combination of cooling tubes 18 integrated in the stack 17 with external cooling tubes 18 as shown in FIG. 4 is another possible flexible variant. In addition to the design reminiscent of flat burners, circular, ring-shaped or hexagonal shapes for the stack 17 or also floor plans are possible, which require a specific installation situation if the supply of air and fuel is ensured.

The fuel preparation takes place in such a way that the heat released at the fuel cell is used directly for the endothermic process of fuel preparation. Reforming is common today when using natural gas. The arrangements shown in FIG. 4 and the arrangements described above are also suitable for integrating the reforming into the stack 17. For this purpose, only the number of cooling tubes 18, which are necessary to cover the heat requirement of the reforming, are filled with catalyst material. In coal or biomass gasification, allothermal gasification is a suitable process and here the cooling pipes 18 or the post-combustion chamber 8 serve as a heat source for the allothermal gasification.

A further developed embodiment of a cooler integrated in the stack consists of an insulating tube 22, which is closed on the outlet side of the stack 17 and is arranged in central positions parallel to the heat-defying fuel cell tubes 100 in the stack, as shown in FIG. 5. Arranged in this tube 22, which is closed on the outlet side, is a second tube 24 which is open on the inside and which supplies the arrangement with cooling gas. The inner tube is arranged centrally in the outer tube so that the between the tubes 22, 24 resulting annular gap is sufficient to ensure a functional discharge of the cooling gas. In one variant, the cooling gas is combustion air as cathode gas 2 a, which after heating up flows into the air box 16 and then to the cathode side of the fuel cell tubes 100. In another variant, not shown in FIG. 5, natural gas or another hydrocarbon-containing fuel gas that flows in via the pipe 24 is the cooling gas. Here, the tube arrangement consisting of tubes 22 and 24, in which the pre-reforming now takes place, is provided with catalyst material and the pre-deformed fuel gas flows through suitable openings in the outer tube 22, which are arranged on the inlet side of the stack 17, to the anode side of the fuel cell tubes 100. This arrangement is gas-tightly separated from the air side, in particular from the air box 16.

6 shows a detail of the structure of a fuel cell tube 100 which is applied to a carrier tube 19. To produce the fuel cell tube 100, it is advantageous to use a continuous, porous carrier tube 19 made of non-conductive material with the same thermal expansion as the electrolyte 23 Apply the individual fuel cell elements with coatings made of material of the cathodes 2, the electrolyte 23 and the anodes 3 to the support tube 19 one after the other by means of a suitable thin-film or sintering technique. The individual cell elements located one behind the other in this way are electrically connected in series by means of suitably applied gas-tight connection contacts 5.

A useful further development is a partially electrically conductive carrier tube, which is formed from a chain of tube elements made of the material of the cathodes 2, which are connected to the carrier tube by means of annular elements 20 made of electrically insulating material with approximately the same thermal expansion as the electrolyte 23 using a suitable joining technique , as shown in Fig. 7a. The outer surfaces of the tubular elements are provided with a thin gas-tight layer made of material of the electrolyte 23 except for a small annular section at the end of each tubular element made of material of the cathodes 2, which remains free. The portion of the tube surface provided with electrolyte material is with the material of the anodes 3 coated. The individual cell elements which are formed one behind the other in this way are electrically connected in series by means of suitably applied gas-tight connection contacts 5 in order to form the fuel cell tube 100. The part of the cathode 2 that remains free is connected to the anode 3 of the next tubular element, as shown in FIG. 7b.

An advantageous further development is shown in FIGS. 8a and 8b. It is advantageous to design the tubular elements from the material of the cathodes 2 in such a way that the internal cross-section 21 increases the conductor cross section of the tubular element. With the same conductor cross-section, this permits thinner wall thicknesses of the construction and thus smaller diffusion paths for the combustion air and, during start-up operations, higher permissible temperature change rates than is possible with ordinary pipes. The annular element 20 made of electrically insulating material, which is necessary for the construction of the partially electrically conductive carrier tube, is designed such that it is provided on both sides with a number of pin-shaped fitting elements 27, which fit into the inner ribs 21 of the tubular element made of cathode material and using suitable technology are decreed.

A further advantageous development of a fuel cell device is shown in FIG. 9. There, the formation of gas channels 25 parallel to the central axis of the cell elements 1 is provided in the outer nickel felt 4, inner rings 26 or porous tubes made of nickel material being introduced in such a way that they exert a slight contact pressure when heated exert on the nickel felt 4 and thus improve the contact between the nickel felt 4 and the anode side of the fuel cell tube 1.

Claims

claims

1. Fuel cell device with high-temperature fuel cells, characterized in that rotationally symmetrical fuel cells, which are designed in particular as cell elements (1), inside on the side of

Combustion air as cathode gas (2a) and combustion gas as anode gas (3a) on the outside of the anodes (3) and that the fuel cells on the outside of the anode side are completely coated with a high-temperature-resistant, conductive metal felt such as nickel felt (4) or the like be contacted and thereby form a voltage level.

2. Fuel cell device according to claim 1, characterized in that the main flow direction of the fuel gas is guided parallel to the tube axis of the cell elements (1) and optionally a direct current or countercurrent arrangement is provided.

3. Fuel cell device according to claims 1 and 2, characterized in that for a uniform distribution of the fuel gas flow resistance elements are provided at the inlet and or a fuel injection at several locations.

4. Fuel cell device according to claims 1 to 3, characterized in that the individual cell elements (1) of a voltage level with the cell elements (1) of the next voltage level are connected gas-tight by annular connection contacts (5) and that the side of the cathodes (2) of the Stacking element of voltage level n is in contact with the side of the anodes (3) of the stacking element of voltage level n + 1 via the connection contacts (5) and the fuel cell tube (100) is thus formed.

5. Fuel cell device according to one or more of claims 1 to 4, characterized in that the sides of the anodes (3) of the individual stacking elements are electrically separated from one another so that a gas-permeable intermediate floor (6) made of insulator material, which is designed in particular as a nozzle floor (12), with corresponding passages for the fuel cell tubes (100) is inserted between the individual stacking elements or spacers made of insulator material are used which prevent a short circuit between two voltage levels.

6. Fuel cell device according to claim 5, characterized in that the fuel cell tubes (100) through the intermediate floors (6) are not clamped, but are free to move to prevent possible expansion problems from the outset.

7. Fuel cell device according to one or more of claims 1 to 6, characterized in that the cell elements (1) of the first group of stack elements on the air side are fitted gas-tight in a perforated plate (7) so that the combustion air as cathode gas (2a) in the fuel cell tubes (1) can flow in without coming into contact with the fuel gas as anode gas (3a).

8. Fuel cell device according to one or more of claims 1 to 7, characterized in that the perforated plate (7) made of electrically conductive

Material with the same possible expansion behavior as the fuel cell tubes (100) consists (lanthanum chromite) and is conductively connected to the anodes (3) of the fuel cell tubes (100).

9. Fuel cell device according to one or more of claims 1 to 8, characterized in that the serial circuit of the fuel cell tubes (100) on the perforated plate (7) with a correspondingly changed circuit of the fuel cell tubes (100) begins with a cathode-side contacting and insulation between the perforated plate (7) and the high temperature resistant, electrically conductive metal felt is used.

10. Fuel cell device according to one or more of claims 1 to 9, characterized in that the outlet of anode gas (3a) and Cathode gas (2a) from the stack (17) of the fuel cell tubes (100) is designed such that both gas flows are led to the afterburning chamber (8).

11. Fuel cell device according to one or more of claims 1 to 8 and 10, characterized in that the anode gas space is first electrically isolated by a gas-permeable intermediate floor (9) or spacers made of insulator material for electrons to the outside to the outlet connection contact (10).

12. Fuel cell device according to one or more of claims 1 to 8, 10 and 11, characterized in that the cathode side at the outlet of each fuel cell tube (100) of the last voltage level for contacting is provided with nozzle-shaped outlet connection contacts (10) which exits at the tube the connection to the current drain (11) of the

Make the stack (17).

13. Fuel cell device according to one or more of claims 1 to 8 and 10, 11, 12, characterized in that the connection between the respective outlet connection contact (10) and the adjacent one

Fuel cell tubes (100) is arranged so that it is always wetted with anode gas (3a) and therefore oxidation is excluded.

14. Fuel cell device according to one or more of claims 1 to 13, characterized in that nickel felt (4) or a high-temperature-resistant conductive metal felt is used as the material for current dissipation

15. Fuel cell device according to one or more of claims 1 to 14, characterized in that within the nickel felt (4) or

Metal felt additional rigid current leads are movably attached to minimize the resistance of the lead.

16. Fuel cell device according to one or more of claims 1 to

15, characterized in that the stack construction at the outlet of the fuel cell tubes (100) is completed by the conductive nozzle base (12) or a conductive network.

17. Fuel cell device according to one or more of claims 1 to

16, characterized in that the outlet connection contacts (10) and the conductive nozzle base (12) are designed and arranged such that nitrogen oxide formation during the combustion of the anode gas (3a) is largely excluded.

18. Fuel cell device according to one or more of claims 1 to 7, 9 to 11, characterized in that the anode side at the outlet of each fuel cell tube (100) of the last voltage level by contacting the high-temperature-resistant felt, the connection to

Current discharge (11) of the stack.

19. Fuel cell device according to one or more of claims 1 to 7, 9 to 11 and 18, characterized in that rigid current leads are movably attached within the high temperature resistant felt at the outlet.

20. Fuel cell device according to one or more of claims 1 to 7, 9 to 11 and 18 to 19, characterized in that the outlet side of the fuel cell pipes (100) and the conductive nozzle base (12) are designed and arranged so that the nitrogen oxide formation in the Combustion of the anode gas (3a) is largely excluded.

21. Fuel cell device according to one or more of claims 1 to 20, characterized in that in the counterflow arrangement (Fig. 3a), the fuel gas is added as anode gas (3a) in the area of the air outlet and the outlet area of the combustion air is designed as cathode gas (2a) that the current discharge on the cathode side - gastight - separates the cell area and the exit area so that there is no mixing of anode exhaust gas and fresh fuel gas

22. Fuel cell device according to one or more of claims 1 to 21, characterized in that the fresh fuel gas against the

Flow of the combustion air is led along to the air inlet and there the fuel gas / product gas mixture formed during the combustion reaction is diverted and guided through channels, which are also tubular, to the area of the air outlet and is burned with the fuel gas residue in the afterburning chamber (8).

23. Fuel cell device according to one or more of claims 1 to

22, characterized in that in the counterflow arrangement (Fig. 3a) a separate removal of anode-side exhaust gas and the exhaust air from the cathode side is provided and the removal of the exhaust air (2b) and the anode-side exhaust gas (3b) takes place via separate channels

24. Fuel cell device according to one or more of claims 1 to

23, characterized in that the stack (17) is closed to the side (13) in such a way that there is no short circuit between the individual

Voltage levels can occur and continuous ceramic walls or combinations of metallic walls with ceramic insulation pieces are used in the transition area between the individual voltage levels.

25. Fuel cell device according to one or more of claims 1 to

24, characterized in that the combustion air is supplied as a cathode gas (2a) from a supply line (14) to an air box (16) and from there enters the cathode side of the fuel cell tubes (100)

26. Fuel cell device according to one or more of claims 1 to

25, characterized in that the fuel gas as anode gas (3a) a fuel gas line (15) is guided laterally at several points and / or via separate nozzles in the perforated plate (7) into the stack (17).

27. Fuel cell device according to one or more of claims 1 to 26, characterized in that the stack (17) similar to a

Flat burner is built.

28. Fuel cell device according to one or more of claims 1 to 27, characterized in that circular, annular or hexagonal shapes for the stack (17) or almost any floor plan are possible if the installation situation requires it and the supply of air and fuel are ensured can.

29. Fuel cell device according to claims 1 to 28, characterized in that the post-combustion chamber (8) as a common

Combustion chamber is formed.

30. Fuel cell device according to one or more of claims 1 to 29, characterized in that cooling tubes (18) are arranged on the stack (17) as radiation coolers.

31. Fuel cell device according to claim 30, characterized in that the cooling tubes (18) are guided parallel to the fuel line tubes (100) in the stack (17) and to avoid short circuits in the stack (17) consist of insulator material.

32. Fuel cell device according to one or more of claims 1 to

31, characterized in that a combination of cooling tubes (18) integrated in the stack (17) with external cooling tubes (18) is used.

33. Fuel cell device according to one or more of claims 1 to

32, characterized in that the released at the fuel cell Heat is used directly for the endothermic process of fuel processing and the number of cooling tubes (18) that are required to cover the heat requirement of the fuel processing are filled with catalyst material.

34. Fuel cell device according to one or more of claims 1 to 33, characterized in that a cooler integrated in the stack (17) consists of an externally electrically insulating tube (22) (FIG. 5), which on the outlet side of the stack (17) is closed and is arranged in central locations parallel to the heat-emitting fuel cell tubes (100) in the stack (17), and that in this tube (22) which is closed on the outlet side, a second tube (24) which is open on the outlet side is arranged, which arrangement supplied with cooling gas, and that the inner tube (24) is arranged centrally in the outer tube (22) so that the annular gap which arises between the tubes (22, 24) is sufficient to ensure proper functioning

Ensure the cooling gas flows out.

35. Fuel cell device according to claim 34, characterized in that the cooling gas as combustion air is the cathode gas (2a), which after heating in the air box (16) and then to the cathode side of the

Fuel cell pipes (1) flows.

36. Fuel cell device according to claim 34, characterized in that the cooling gas is natural gas or another hydrocarbon-containing fuel gas which flows in via the pipe (24), that the pipe arrangement consisting of the

Tubes (22) and (24), in which the pre-reforming now takes place, is provided with catalyst material that the pre-reformed fuel gas via suitable openings in the outer tube (22), which are arranged on the inlet side of the stack (17), to the anode side of the fuel cell tubes (100) flows and that this arrangement gas-tight from the air side, in particular the

Air box (16) is separated.

37. Fuel cell device according to one or more of claims 1 to

36, characterized in that when coal or biomass gasification is used in an allothermal gasification, the tubes (18) and / or the post-combustion chamber (8) heated by the stacks (17) serve as a heat source for the allothermal gasification.

38. Fuel cell device according to one or more of claims 1 to

37, characterized in that a continuous porous support tube (19) (Fig. 6) made of an electrically non-conductive material with the same thermal expansion as the electrolyte material and that on this support tube, the cathodes (2), the electrolytes (23) and Anodes (3) as separate cell elements and the connection contacts (5) between the individual cell elements are applied in layers by means of a suitable thin-layer technique and / or sintering technique.

39. Fuel cell device according to one or more of claims 1 to

38, characterized in that a partially electrically conductive support tube (Fig. 7a), which is formed from a chain of tube elements made of cathode material which by means of annular elements (20) made of electrically insulating material with approximately the same thermal expansion as the electrolyte (23) with a suitable joining technology to the tube, and that the outer surfaces of the tubular elements are provided with a thin gas-tight layer of material of the electrolyte (23) except for a small annular portion at the end of each tubular element made of cathode material, which remains free that the electrolyte material provided portion of the

Pipe surface is coated with anode material and that the individual cell elements formed one behind the other are electrically connected in series by means of suitably applied gas-tight connection contacts (5) in order to form the fuel cell (100) (FIG. 7b).

40. Fuel cell device according to claim 39, characterized in that the tubular elements are made of cathode material so that the internal cross-section (21) (Fig. 8a) of the conductor cross section of the tubular element enlarged and / or that the ring-shaped element (20) necessary for the construction of the partially electrically conductive support tube (19) is made of electrically insulating material so that it is provided on both sides with a number of pin-shaped fitting elements (27) which extend into the interior Ribs (21) of the tubular element made of cathode material are fitted and have (Fig. 8b).

41. Fuel cell device according to one or more of claims 1 to

40, characterized in that to the fuel cell pipes (100) parallel gas channels (25) (Fig. 9) are formed in the outer nickel felt (4), wherein inner rings (26) or porous pipes made of nickel material are introduced so that they improve the When heating the contact between the nickel felt (4) and the anode side of the fuel cell tube (100), exert a slight pressure on the nickel felt (4).

42. Fuel cell device according to one or more of claims 1 to

41, characterized in that the cathode (2) is on the outside and the anode (3) on the inside of the fuel cell tube (100)

43. Fuel cell device according to one or more of claims 1 to

42, characterized in that the production of individual tension levels, each provided with the associated gas-permeable intermediate floors (9) (FIG. 2), consists of the required number of cell elements (1), nickel felt (4) and inner rings (26), which soaked in volatile plastic or water glass give a compact block that the gas-tight cell elements (1) are designed so that they are equipped with a contact surface on the cathode (2) and anode (3), as well as the necessary insulation and that the assembly to the fuel cell tubes (100) is then carried out in all tubes of the stack (17) in one operation per voltage level by using a suitable

Joining process the associated cell elements are electrically connected in series and gas-tight.

44. Fuel cell device according to one or more of claims 1 to 43, characterized in that the cell elements (1) which form the fuel cell tube (100) have different lengths in order to enlarge the surfaces of the individual cell elements (1) with increasing use of fuel gas.